Tree root systems are inherently dynamic in their distribution within a soil volume. Analysis of tree root system space occupation through time can improve not only our implicit understanding of a virtually hidden portion of a plant, but influence future management decisions through a more thorough understanding of root placement within a soil volume. We compared root standing crop populations of four ornamental tree species including Acer rubrum L. ‘Franksred’ (Acer), Carpinus betula L. ‘Columnaris’ (Carpinus), Gleditsia tricanthos L. var. inermis ‘Skycole’ (Gleditsia), and Quercus rubra L. ‘Rubrum’ (Quercus) grown in a nursery mix substrate within large 57-L containers using an X-ray computed tomography (CT) approach through time. Individual root identification was performed manually on two-dimensional slices of CT scans. Our data show high variation in species total root number through time with Carpinus exhibiting the largest root population throughout the study period. However, species exhibited differences in root distribution patterns as exemplified by the shallow and horizontally more uniform rooting pattern of Acer in comparison with the highly plastic root distribution in space through time in Gleditsia. Root frequencies within 1-mm root diameter class distributions shifted by species with the most drastic differences found between high frequencies of relatively small diameter roots in Acer vs. pronounced shifts in dominate root diameter size class as found in Gleditsia and lesser so in Carpinus during a growing season. Our findings demonstrate differences in whole tree root systems space occupation non-destructively through time and highlight a disparity in how species fill a container volume during growth.
Spring frosts and subsequent crop losses threaten the economic sustainability of fruit crop producers all over the world. This study used a controlled-freezing technique to impose a post-budburst freezing stress to grapevine shoots forced from one-node cuttings [‘Albariño’, ‘Cabernet Franc’, ‘Cabernet Sauvignon’, and ‘Pinot Grigio’ (Vitis vinifera)] and whole plants [‘Noiret’ (Vitis hybrid)]. Our goal was to investigate the incidence of freeze injury among cultivars, stage of phenological development, and a potassium salt-based fertilizer (KDL) with potential cryoprotectant activity. Among the V. vinifera cultivars, the incidence of mortality of shoots exposed to −3.5 °C was highest for ‘Albariño’ (71%) and lowest for ‘Cabernet Sauvignon’ (51%). Cuttings sprayed with KDL 24 hours before cold temperature exposure exhibited 16% lower shoot mortality and lower osmotic potential (Ψs) (−0.92 MPa) than the unsprayed cuttings (−0.77 MPa). However, application of KDL did not impact shoot mortality for whole ‘Noiret’ vines. Mortality for ‘Noiret’ shoots greatly increased with the advancement of phenological development, ranging from 10% in wooly buds to 78% in shoots ≈10-cm long. The practical significance of KDL remains questionable; cultivar selection still appears to be a more reliable method for avoiding spring frost, by planting late bursting cultivars in more frost-prone areas.